The repair, as well as the replacement, of diseased and damaged human bone have been the subject of substantial research efforts over the past several decades. This research has yielded advances in the reconstruction of many areas of the human skeletal system As a result of these advances, bone replacements and repair are presently being undertaken in several areas including the restructuring of the craniofacial system, bone repair, spinal repair, the introduction of knee and hip joints and ligament replacement.
The biological mechanisms underlying the reconstruction and repair varies according to the type of bone implant selected. New bone can be formed by three basic mechanisms: osteogenesis, osteoconduction and osteoinduction. In osteogenic transplantation, viable osteoblasts and osteoclasts are moved from one body location to another where they establish centers of bone formation. Autograft tissue, cancerous bone and marrow grafts provide such viable cells. As a generalization, spongy cancerous bone permits rapid and usually complete reossification.
In the transplantation of large segments of allogenic banked bone, direct osteogenesis does not occur. In these cases, osteoconduction transpires—the dead bone acts as a scaffold for the ingrowth of blood vessels, followed by the resorption of the implant and deposition of new bone. This process is slow, sometimes requiring years to reunite a large segmental defect. As a generalization, cortical bone has high strength and undergoes osteoclastic digestion of the bone and revascularizes through pre-existing anatomical channels, a relatively slow process.
Osteoinduction is the phenotypic conversion of connective tissue into bone by an appropriate stimulus. As this concept implies, formation of bone can be induced at even non-skeletal sites. Osteoinduction is the preferred method of providing new bone growth as allografts of this type are typically incorporated into the host bone within several weeks. In contrast, some osteoconductive grafts have been found to be non-incorporated as long as one year after implantation.
In order to provide an environment suitable for osteoinduction, a material should be selected which is not only capable of inducing osteogenesis throughout its volume, but is also biocompatible, non-inflammatory, and possesses the ability to be ultimately resorbed by the body and replaced with new, natural bone. Demineralized bone is osteoinductive and when used in surgery by a physician is quite often mixed with marrow retrieved from the patient at the time of surgery.
In most bone marrow collecting procedures, multiple aspirations of bone marrow are required to enable enough bone marrow to be collected to perform a bone marrow transplant to the surgical site or be mixed with the osteoinductive material being used at the surgical site. Bone marrow density can and does vary from patient to patient and there is no uniform viscosity to bone marrow. Younger healthy patients often have denser thicker marrow. Usually thicker marrow is the result of more trabecula tissue present in the cavity. All of these bone marrow collecting procedures require that the bone be punctured in order to access the bone marrow within. Generally bone marrow aspiration is accessed via an open wound, most typically by exposing the iliac crest. In many instances, the instrument tip is difficult to fix into the bone as it skates over the curved hard irregular surface of the iliac crest. Thus, it is important to provide an instrument which enhances the ability of the user to easily puncture bone and obtain bone marrow with minimal trauma to the patient.
The bone marrow removal procedure is quite painful to the patient and requires much exertion and care by the physician in operating the instrument. Early problems with biopsy needles involved the sharpness of the cannula and trocar and the gripping means used so that the needle could be placed accurately and the bone could be penetrated quickly. U.S. Pat. No. 4,356,828, for example, discloses an improved finger gripping member and U.S. Pat. No. 4,403,617 discloses particular cutting edge configurations for the trocar and cannula. Developments in the gripping means of the trocar and cannula continued with emphasis being placed on the secure engagement of the trocar within the cannula and ease of use for the physician.
All bone marrow biopsy, aspiration and transplant needles or cannulas currently on the market have a handle with a cannula extending outwardly from the handle. The handle is used by the surgeon to apply force to the cannula as the cannula penetrates the bone. Such needles typically include a stylet with a sharpened tip which is inserted through the cannula and is used to initially penetrate the bone. The stylet also serves to occlude the cannula while the bone is penetrated, so that the marrow sample subsequently taken is free from bone chips. The stylet is then removed and bone marrow is withdrawn from the patient by manipulating the cannula to cause bone marrow to move into the interior of the cannula. In some cases a slight suction is applied to the cannula to hold the bone marrow specimen within the cannula as the device is removed from the patient or a syringe can be attached to the cannula to remove the bone marrow as is shown in U.S. Pat. No. 4,838,282.
Previous prior art biopsy or collection instruments have grips which do not really fit into the physician's hand to provide for positive gripping by the physician but have grips which are required to be engaged by the physician in a negative way making the process of biopsy or bone marrow collection uncomfortable to the physician/surgeon using the instrument. The handles of the bone marrow collection instrument must securely engage into the physician's or surgeon's palm for optimum control of the instrument during a biopsy or surgery and be easily grasped by the fingers of the user. It is also necessary that the stylet and cannula be engaged to each other during the surgical process for providing total control to the physician or surgeon.
Prior art needles have secured cannula tubes into the cannula housing in numerous ways providing increased manufacturing processes, resulting in an increased end cost to the patient.
The present invention overcomes the disadvantages of the prior art references by providing a bone marrow aspiration instrument having a winged cannula handle and detent locking between the stylet handle and cannula handle.
Bone marrow needles have traditionally been designed so that the needle is attached to the center of the handle. While many physicians feel comfortable with a centrally attached needle, it has been discovered that it may be easier to guide a needle with a user's index finger when the needle is not centrally located on the handle of the needle assembly. It has also recently been discovered that when an off-center device is used, it is important to insure that a physician's arm, wrist, and index finger are all generally in alignment with the cannula of the needle to provide enhanced control over the needle. Examples of such devices are described in U.S. Pat. No. 4,469,109.
Another disadvantage of most bone marrow instruments currently on the market is that when the stylet is removed from the cannula, the shape of the handle typically is materially changed. For example, the bone marrow needle assembly described in U.S. Pat. No. 4,838,282 involves removing approximately half of the handle assembly when the stylet is removed from the cannula. It is desirable to maintain substantially the original shape of the handle after the stylet has been removed to allow a physician to more easily manipulate the cannula within a patient's bone.